"There's a big overhang on CPC, a lot was added to the programme and everyone was covered already," one trader said.

On Monday, the Kazakh CPC Blend differential fell after an updated loading programme was issued showing that March exports would be boosted to 3.26 million metric tons, up from the initial program of 3.02 million metric tons.

Refining margins have improved of late but the outlook is bearish, the same trader said, as benchmark dated Brent is anticipated to firm with the return of Asian refineries from maintenance as they will buy benchmark grades.

Pumping through the unreliable Kirkuk-Ceyhan pipeline has been stopped since March 2, a regional shipping source said on Tuesday.

Libya's NOC issued March official selling prices. Es Sharara OSP was set at dated Brent plus 65 cents a barrel in March, down 10 cents a barrel from last month. The Mellitah OSP was set at dated Brent plus 40 cents a barrel, down from dated Brent plus 45 cents a barrel in February.

Prices on the offshore grades were lowered.

Libyan exports are reduced to the offshore and Mellitah terminals.

Libya's defence minister promised protesters at the El Sharara oilfield to look into their demands but it was too early to say when production could resume, oil officials said on Tuesday.

The OPEC producer closed the 340,000 barrels a day-field last month after tribesmen staged a protest at the remote southern location and tribal clashes broke out.